1. Field of the Invention
The present invention relates to disk drives for computer systems. More particularly, the present invention relates to a disk drive employing sector-reconstruction-interleave sectors each storing redundancy data generated in response to an interleave of data sectors.
2. Description of the Prior Art
A disk drive comprises a disk for storing data in radially spaced, concentric tracks. Each track is partitioned into a plurality of data sectors, and user data is written to the disk a sector at a time. A special timing pattern referred to as a preamble as well as a sync mark are recorded at the beginning of each data sector to facilitate synchronizing to the data during read back. A sector level error correction code (ECC), such as a Reed-Solomon code, is also typically employed to detect and correct errors in the data induced by imperfections in the recording and reproduction process. With the sector level ECC, special redundancy symbols are generated over the user data during a write operation and then recorded with the user data in a data sector. During read back, the redundancy symbols are used to detect and correct errors in the user data. However, if the number of errors exceeds the correction power of the sector level ECC, or if the preamble or sync mark in the data sector is unreadable, the data sector becomes unrecoverable at the sector level.
U.S. Pat. No. 5,872,800 discloses track level parity for reconstructing a data sector unrecoverable at the sector level. With the track level parity, each track comprises a parity sector for storing track level parity generated over the data sectors in the track. A data sector unrecoverable at the sector level can be reconstructed at the track level by computing the parity over the other data sectors together with the parity sector.
FIG. 1A shows a prior art disk drive comprising a disk 4, a head 6, and an actuator 8 for actuating the head 6 radially over the disk 4. The disk 4 comprises a plurality of radially spaced, concentric data tracks each comprising a plurality of data sectors (e.g., D0-D14) and a track level parity (TP) sector. The disk 4 is partitioned into a plurality of zones (e.g., inner zone 10 and outer zone 12) wherein the data rate is increased from the inner to outer zones in order to achieve a more constant linear bit density. As shown in FIG. 1B, each data sector comprises a preamble field 14 and a sync mark field 16 for use in synchronizing to user data stored in a data field 18. ECC redundancy symbols 20 are appended to the end of the data sector and used to detect and correct errors in the user data during read back. The TP sector stores parity data generated over the data stored in the data sectors (e.g., D0-D14). The TP sector also stores a TP status bit S 22 which indicates the validity of the TP sector.
A drawback with the ""800 patent is that the correction power of a single parity sector is limited, particularly if multiple consecutive data sectors become unrecoverable at the sector level (due, for example, to a long medium defect).
There is, therefore, a need to improve the track level error recovery in disk drives where multiple consecutive data sectors may become unrecoverable at the sector level.
The present invention may be regarded as a disk drive comprising a disk, a head, and an actuator for actuating the head radially over the disk. The disk comprises a plurality of tracks, each track comprises a plurality of data sectors for storing data and a plurality of sector-reconstruction-interleave (SRI) sectors for storing redundancy data. The redundancy data stored in a selected one of the SRI sectors is generated in response to the data stored in an interleave of the data sectors corresponding to the selected one of the SRI sectors.
In one embodiment, the redundancy data stored in at least one of the SRI sectors is generated by computing a parity over the data stored in an interleave of the data sectors. In another embodiment, the data stored in each interleave of the data sectors represent data polynomials, and the redundancy data stored in the SRI sectors is generated by dividing the data polynomials by a generator polynomial. In yet another embodiment, at least one of the tracks further comprises a sector-reconstruction-all (SRA) sector for storing redundancy data generated in response to the data stored in at least two of the interleaves of the data sectors of the track. In one embodiment, the SRA sector is used to verify a data sector reconstructed using at least one of the SRI sectors.
The present invention may also be regarded as a disk drive comprising a disk comprising a plurality of tracks, each track for storing a plurality of data sectors and a plurality of sector-reconstruction-interleave (SRI) sectors. The disk drive further comprises a head, an actuator for actuating the head radially over the disk, and a disk controller. The disk controller for writing data to the data sectors, generating redundancy data in response to the data stored in an interleave of the data sectors, and writing the redundancy data to a respective SRI sector.
The present invention may also be regarded as a disk controller for use in a disk drive. The disk drive comprising a disk comprising a plurality of tracks, each track for storing a plurality of data sectors and a plurality of sector-reconstruction-interleave (SRI) sectors, a head, and an actuator for actuating the head radially over the disk. The disk controller comprising a means for writing data to the data sectors, a means for generating redundancy data in response to the data stored in an interleave of the data sectors, and a means for writing the redundancy data to a respective SRI sector.